Filter Asterisk: Add AUTH_UNKNOWN_DOMAIN error to list

 * I have been seeing bruteforcing attempts where asterisk fails with
   AUTH_UNKNOWN_DOMAIN (Not a local domain)
Filter Asterisk: Add sample log entry to testcase.

 * Sample log entry for AUTH_UNKNOWN_DOMAIN (Not a local domain)
Merge pull request #244 from clopez/filter-asterisk

Filter Asterisk: Add AUTH_UNKNOWN_DOMAIN error to list